U.S. patent application number 11/506372 was filed with the patent office on 2008-02-21 for methods for releasably attaching sacrificial support members to microfeature workpieces and microfeature devices formed using such methods.
This patent application is currently assigned to Micron Technology, Inc.. Invention is credited to Michael B. Ball, William A. Polinsky.
Application Number | 20080044985 11/506372 |
Document ID | / |
Family ID | 39101860 |
Filed Date | 2008-02-21 |
United States Patent
Application |
20080044985 |
Kind Code |
A1 |
Polinsky; William A. ; et
al. |
February 21, 2008 |
Methods for releasably attaching sacrificial support members to
microfeature workpieces and microfeature devices formed using such
methods
Abstract
Methods for releasably attaching sacrificial support members to
microfeature workpieces and microfeature devices formed using such
methods are disclosed herein. One embodiment, for example, is
directed to a method for processing a microfeature workpiece
releasably attached to a first support member. The workpiece
includes a microelectronic substrate, a plurality of
microelectronic dies on and/or in the substrate, and a sacrificial
support member attached to an active side of the substrate. The
method can include separating individual dies from the workpiece by
cutting through the sacrificial support member and the substrate
while the workpiece is attached to the first support member. The
method can also include attaching a singulated die and
corresponding portion of the sacrificial support member as a unit
to a second support member. The method can further include removing
the sacrificial support member from the die attached to the second
support member with a removal solution that attacks a material of
which the sacrificial support member is composed.
Inventors: |
Polinsky; William A.;
(Meridian, ID) ; Ball; Michael B.; (Boise,
ID) |
Correspondence
Address: |
PERKINS COIE LLP;PATENT-SEA
PO BOX 1247
SEATTLE
WA
98111-1247
US
|
Assignee: |
Micron Technology, Inc.
Boise
ID
|
Family ID: |
39101860 |
Appl. No.: |
11/506372 |
Filed: |
August 17, 2006 |
Current U.S.
Class: |
438/460 |
Current CPC
Class: |
H01L 2924/14 20130101;
H01L 2224/83191 20130101; H01L 24/85 20130101; H01L 2224/85001
20130101; H01L 2924/07802 20130101; H01L 21/6835 20130101; H01L
2224/48091 20130101; H01L 2224/48227 20130101; H01L 2224/2919
20130101; H01L 2224/83855 20130101; H01L 2924/0665 20130101; H01L
2924/01006 20130101; H01L 2924/00014 20130101; H01L 2924/014
20130101; H01L 2924/0665 20130101; H01L 2924/1433 20130101; H01L
2924/15174 20130101; H01L 2924/3025 20130101; H01L 24/48 20130101;
H01L 2224/83191 20130101; H01L 2924/3512 20130101; H01L 24/29
20130101; H01L 2224/48235 20130101; H01L 2924/01005 20130101; H01L
24/83 20130101; H01L 2224/2919 20130101; H01L 2924/00014 20130101;
H01L 2224/2919 20130101; H01L 2924/01033 20130101; H01L 2924/01082
20130101; H01L 2924/00014 20130101; H01L 2924/00 20130101; H01L
2224/78 20130101; H01L 2224/83101 20130101; H01L 2924/0665
20130101; H01L 2224/45099 20130101; H01L 2924/00 20130101; H01L
2924/00014 20130101; H01L 2224/05599 20130101; H01L 2924/00
20130101; H01L 2924/00 20130101; H01L 2221/68354 20130101; H01L
21/78 20130101; H01L 2224/83101 20130101; H01L 2224/48091 20130101;
H01L 2924/00014 20130101; Y10S 438/977 20130101; H01L 2924/0665
20130101 |
Class at
Publication: |
438/460 |
International
Class: |
H01L 21/00 20060101
H01L021/00 |
Claims
1. A method for processing a microfeature workpiece releasably
attached to a first support member, the workpiece including a
microelectronic substrate, a plurality of microelectronic dies on
and/or in the substrate, and a sacrificial support member attached
to an active side of the substrate over the dies, the method
comprising: separating individual dies from the workpiece by
cutting through the sacrificial support member and the substrate
while the workpiece is attached to the first support member;
attaching a singulated die and corresponding portion of the
sacrificial support member as a unit to a second support member;
and removing the sacrificial support member from the die attached
to the second support member with a removal solution that attacks a
material of which the sacrificial support member is composed.
2. The method of claim 1 wherein removing the sacrificial support
member from the die attached to the second support member with a
removal solution comprises at least partially immersing the die and
second support member into a bath of removal solution.
3. The method of claim 2 wherein removing the sacrificial support
member from the die attached to the second support member with a
removal solution comprises at least partially immersing the die and
second support member into a bath including an acetone
material.
4. The method of claim 1 wherein removing the sacrificial support
member from the die attached to the second support member with a
removal solution comprises disposing the removal solution onto at
least a portion of the sacrificial support member using a spraying
process.
5. The method of claim 1 wherein removing the sacrificial support
member with a removal solution comprises dissolving at least
approximately all the sacrificial support member.
6. The method of claim 1 wherein removing the sacrificial support
member with a removal solution comprises dissolving a portion of
the sacrificial support member such that the bond between the die
and the sacrificial support member fails and the remaining portion
of the sacrificial support member is removed from the die.
7. The method of claim 1 wherein the individual dies include
integrated circuitry and pads electrically coupled to the
integrated circuitry, and wherein the method further comprises
forming a plurality of wire bonds between the pads on the die and
corresponding contact pads on the second support member after
removing the sacrificial support member from the die.
8. The method of claim 1 wherein the sacrificial support member is
a generally flowable support material when initially applied to the
substrate, and wherein the method further comprises: curing the
generally flowable support material to a desired rigidity to form
the sacrificial support member after applying the support material
on the substrate; and removing material from a back side of the
substrate to thin the substrate after curing the support material
and before releasably attaching the workpiece to the first support
member.
9. The method of claim 1 wherein attaching a singulated die and
corresponding portion of the sacrificial support member as a unit
to a second support member comprises attaching a singulated die to
a lead frame, an interposer substrate, a circuit board, or flex
tape.
10. The method of claim 1, further comprising forming a plurality
of apertures in the sacrificial support member before separating
individual dies from the workpiece.
11. The method of claim 10 wherein forming a plurality of apertures
in the sacrificial support member comprises forming a plurality of
apertures that extend only partially through the sacrificial
support member.
12. The method of claim 10 wherein forming a plurality of apertures
in the sacrificial support member comprises forming a plurality of
apertures that extend completely through the sacrificial support
member to the active side of the substrate.
13. The method of claim 1 wherein separating individual dies from
the workpiece while the workpiece is attached to the first support
member comprises separating individual dies from the workpiece
while the workpiece is attached to a dicing frame.
14. The method of claim 1 wherein attaching a singulated die and
corresponding portion of the sacrificial support member as a unit
to a second support member comprises attaching the die to the
second support member with an adhesive material.
15. The method of claim 14 wherein attaching the die to the second
support member with an adhesive material comprises (a) attaching
the die to the second support member with an epoxy material, and
(b) at least partially curing the epoxy material before removing at
least approximately all the sacrificial support member from the
die.
16. The method of claim 1 wherein separating individual dies from
the workpiece by cutting through the sacrificial support member and
the substrate includes: cutting through the sacrificial support
member with a first wafer saw having a first blade coarseness; and
cutting through the substrate with a second wafer saw having a
second blade coarseness less than the first blade coarseness.
17. A method for processing a microfeature workpiece having a
substrate and a plurality of microelectronic dies on and/or in the
substrate, the individual dies including integrated circuitry and
pads electrically coupled to the integrated circuitry, the method
comprising: attaching a sacrificial support member to an active
side of the substrate and over the dies; releasably attaching a
back side of the substrate to a dicing frame; separating individual
dies from the workpiece by cutting through the sacrificial support
member and the substrate while the substrate is attached to the
dicing frame; removing the singulated dies and corresponding
portions of the sacrificial support member from the dicing frame;
adhesively attaching one or more singulated dies to a support
member; and removing the sacrificial support member from each die
attached to the support member with a solvent that attacks a
material of which the sacrificial support member is composed.
18. The method of claim 17, further comprising removing material
from the back side of the substrate to thin the substrate after
attaching the sacrificial support member to the active side and
before releasably attaching the back side to the dicing frame.
19. The method of claim 18 wherein removing material from a back
side of the substrate to thin the substrate includes thinning the
substrate to a thickness of approximately 50-100 .mu.m.
20. The method of claim 18, further comprising applying a wafer
treatment to the back side of the substrate after removing material
from the back side and before releasably attaching the back side to
the dicing frame.
21. The method of claim 17 wherein attaching a sacrificial support
member to an side of the substrate and over the dies comprises:
depositing a generally flowable support material onto the active
side of the substrate; and curing the support material to a
generally non-flowable state and a desired rigidity to form the
sacrificial support member.
22. The method of claim 21 wherein depositing a generally flowable
support material onto the active side of the substrate comprises
depositing a polymeric or ceramic support material.
23. The method of claim 21 wherein depositing a generally flowable
support material onto the active side of the substrate comprises
depositing the support material using spin-on techniques, screen
printing processes, spraying techniques, brushing techniques,
molding, a dip bath, or lamination.
24. The method of claim 17 wherein attaching a sacrificial support
member to an active side of the substrate and over the dies
comprises attaching a generally rigid, sacrificial support member
to the active side of the substrate with an adhesive material.
25. The method of claim 17 wherein attaching a sacrificial support
member to the active side of the substrate and over the dies
comprises attaching a sacrificial support member having a
coefficient of thermal expansion (CTE) at least generally similar
to the CTE of the substrate.
26. The method of claim 17, further comprising forming a plurality
of openings extending at least partially through the sacrificial
support member before separating individual dies from each
other.
27. The method of claim 26 wherein forming a plurality of openings
extending at least partially through the sacrificial support member
occurs before attaching the sacrificial support member to the
active side of the substrate.
28. The method of claim 26 wherein the individual dies on and/or in
the substrate are separated from each other by a plurality of
streets, and wherein: forming a plurality of openings extending at
least partially through the sacrificial support member comprises
creating a plurality of openings that extend only partially through
the sacrificial support member and are out of alignment with the
streets between the individual dies.
29. The method of claim 17 wherein removing the sacrificial support
member from each die attached to the support member with a solvent
comprises selecting a solvent that does not generally affect the
bond between the individual dies and the support member.
30. The method of claim 17 wherein removing the sacrificial support
member from each die attached to the support member with a solvent
comprises at least partially immersing the one or more dies and
support member into a solvent bath.
31. The method of claim 30 wherein removing the sacrificial support
member from each die attached to the support member with a solvent
comprises at least partially immersing the one or more dies and
support member into a bath of acetone material.
32. The method of claim 30 wherein removing the sacrificial support
member from each die attached to the support member with a solvent
comprises disposing the solvent onto the sacrificial support member
carried by the one or more dies using a spraying process.
33. The method of claim 17 wherein removing the sacrificial support
member from each die attached to the support member with a solvent
comprises dissolving at least approximately all the sacrificial
support member from each die.
34. The method of claim 17 wherein removing the sacrificial support
member from each die attached to the support member with a solvent
comprises dissolving a portion of the sacrificial support member
from each die such that the bond between the die and the
sacrificial support member fails and the remaining portion of the
sacrificial support member is removed from the die.
35. The method of claim 17 wherein adhesively attaching one or more
singulated dies to a support member comprises attaching one or more
dies to a lead frame, an interposer substrate, a circuit board, or
flex tape.
36. The method of claim 17 wherein adhesively attaching one or more
singulated dies to a support member comprises (a) attaching the one
or more dies to the second support member with an epoxy material,
and (b) at least partially curing the epoxy material before
removing the sacrificial support member from each die.
37. The method of claim 17, further comprising forming a plurality
of wire bonds between the pads on the one or more dies attached to
the support member and corresponding contact pads on the support
member after removing the sacrificial support member from each die
with the solvent.
38. A method for forming a microfeature device, the method
comprising: supporting a front side of a microfeature workpiece
with a sacrificial support member, the workpiece including a
plurality of microelectronic dies; removing material from a back
side of the workpiece to thin the workpiece from a first thickness
to a second thickness less than the first thickness while the
workpiece is supported by the sacrificial support member;
temporarily supporting the workpiece and the sacrificial support
member with a first support member positioned proximate to the back
side of the workpiece; while the workpiece is temporarily supported
by the first support member, cutting through the sacrificial
support member and the workpiece to separate the individual dies
from each other; adhesively attaching a singulated die and
corresponding portion of the sacrificial support member as a unit
to a second support member; exposing the die and corresponding
portion of the sacrificial support member to a removal solution
that attacks a material of which the sacrificial support member is
formed to remove at least approximately all the sacrificial support
member from the die; and electrically coupling the die to the
second support member after removing at least approximately all the
sacrificial support member.
39. The method of claim 38 wherein removing material from a back
side of the workpiece to thin the workpiece includes thinning the
workpiece to a thickness of approximately 50-100 .mu.m.
40. The method of claim 38 wherein exposing the die and
corresponding portion of the sacrificial support member to a
removal solution comprises at least partially immersing the die and
sacrificial support member into a solvent bath.
41. The method of claim 38 wherein exposing the die and
corresponding portion of the sacrificial support member to a
removal solution comprises exposing the die and sacrificial support
member to a removal solution that does not generally affect the
bond between the die and the second support member.
42. The method of claim 38, further comprising forming a plurality
of openings extending partially through the sacrificial support
member before cutting through the sacrificial support member and
the workpiece to separate the individual dies from each other, the
individual openings being out of alignment with a plurality of
streets between the individual dies.
43. The method of claim 38 wherein adhesively attaching a
singulated die and corresponding portion of the sacrificial support
member as a unit to a second support member comprises attaching one
or more dies to a lead frame, an interposer substrate, a circuit
board, or flex tape.
44. The method of claim 38 wherein the die includes integrated
circuitry and pads electrically coupled to the integrated
circuitry, and wherein: electrically coupling the die to the second
support member comprises forming a plurality of wire bonds between
the pads on the die and corresponding contact pads on the second
support member after removing at least approximately all the
sacrificial support member.
45. A method for processing a microfeature workpiece, the method
comprising: providing a microfeature workpiece including (a) a
microelectronic substrate with a front side and a back side, (b) a
plurality of microelectronic dies at the front side of the
substrate, and (c) a sacrificial support member attached to the
front side over the dies; cutting through the sacrificial support
member and substrate to singulate the dies; attaching a singulated
die and corresponding portion of the sacrificial support member to
a support member with an adhesive material; and removing the
portion of the sacrificial support member from the die with a
solvent that at least partially dissolves the sacrificial support
member such that the bond between the sacrificial support member
and the die fails without generally affecting the adhesive bond
between the die and the support member.
46. The method of claim 45 wherein attaching a singulated die and
corresponding portion of the sacrificial support member to a
support member comprises attaching the die to a lead an interposer
substrate, a circuit board, or flex tape.
47. The method of claim 45, further comprising forming a plurality
of openings extending partially through the sacrificial support
member before cutting through the sacrificial support member and
substrate to singulate the dies.
48. A microfeature assembly, comprising: a microfeature workpiece
including a microelectronic substrate having a front side, a back
side, and a plurality of microelectronic dies at the front side; a
sacrificial support member attached to the front side of the
substrate; and a first support member carrying the substrate and
the sacrificial support member, the first support member being
removably attached to the substrate to temporarily support the
substrate and the sacrificial support member during singulation of
the dies.
49. The microfeature assembly of claim 48 wherein the sacrificial
support member comprises a generally flowable polymeric or ceramic
support material which has been cured to a non-flowable state.
50. The microfeature assembly of claim 48 wherein the sacrificial
support member comprises a generally rigid, sacrificial support
member that is adhesively attached to the front side of the
substrate.
51. The microfeature assembly of claim 48 wherein the substrate has
a thickness of approximately 50-100 .mu.m.
52. The microfeature assembly of claim 48 wherein the first support
member includes a dicing frame.
53. The microfeature assembly of claim 48 wherein the sacrificial
support member has a coefficient of thermal expansion (CTE) at
least generally similar to the CTE of the substrate.
54. The microfeature assembly of claim 48, further comprising a
plurality of openings extending at least partially through the
sacrificial support member.
55. The microfeature assembly of claim 54 wherein the individual
dies are separated from each other by a plurality of streets, and
wherein: the plurality of openings extend only partially through
the sacrificial support member and are out of alignment with the
streets between the individual dies.
56. A microfeature device, comprising: a microelectronic die having
a front side, a back side, integrated circuitry, and a plurality of
pads at the front side electrically coupled to the integrated
circuitry; a sacrificial support member on the front side of the
die, the sacrificial support member including a polymeric or
ceramic support material which is removable from the die with a
solvent; and a second support member adhesively attached to the
back side of the die.
57. The microfeature device of claim 56 wherein the sacrificial
support member comprises a generally flowable material which has
been cured to a non-flowable state and a desired rigidity.
58. The microfeature device of claim 56 wherein the sacrificial
support member is composed of a material that is at least partially
dissolvable upon contact with the solvent such that the bond
between the sacrificial support member and the front side of the
die fails without generally affecting the adhesive bond between the
die and the second support member.
59. The microfeature device of claim 56 wherein the die has a
thickness of approximately 50-100 .mu.m.
60. The microfeature device of claim 56, further comprising a
plurality of openings extending at least partially through the
sacrificial support member.
61. The microfeature device of claim 56 wherein the second support
member comprises a lead frame, an interposer substrate, a circuit
board, or flex tape.
Description
TECHNICAL FIELD
[0001] The present invention is related to methods for releasably
attaching sacrificial support members to microfeature workpieces
and microfeature devices formed using such methods.
BACKGROUND
[0002] Existing microelectronic device packages typically include a
microelectronic die attached to a support member, such as a printed
circuit board. Bond-pads or other terminals on the die are
electrically connected to corresponding terminals on the support
member, for example, with solder balls or wires. The connection
between the die and the support member can be protected by
encapsulating the die to form a device package. The package can
then be electrically connected to other microelectronic devices or
circuits in many types of consumer or industrial electronic
products.
[0003] Manufacturers are under continuous pressure to reduce the
size of the electronic products. Accordingly, microelectronic die
manufacturers seek to reduce the size of the packaged dies
incorporated into the electronic products. The height of the
packaged dies is often reduced by grinding the back side of the
wafer to thin the dies before singulating the wafer and
encapsulating the dies. One drawback with this approach, however,
is that thin wafers are extremely fragile and therefore difficult
to handle after backgrinding.
[0004] One approach for addressing this drawback is to attach a
relatively thick wafer support to the wafer for the grinding
process to ensure survival of the wafer as well as to facilitate
subsequent handling of the wafer for further processing. One
system, for example, includes applying or laminating a generally
flowable material onto an active side of the wafer and then curing
the material to a desired rigidity to form the wafer support. After
backgrinding, the thinned wafer is attached to a vacuum chuck and
the wafer (and attached wafer support) are completely immersed into
a solvent bath to dissolve or otherwise remove the wafer support.
The wafer is then flipped and mounted on a dicing frame with the
active side of the wafer facing downward, after which the wafer is
singulated and the individual dies are removed from the dicing
frame with a conventional pick-and-place apparatus. In several
instances, the wafer can be mounted to the dicing frame before
removal of the wafer support.
[0005] One drawback with the foregoing approach is that the thinned
wafer must undergo a number of additional processing steps after
the wafer support is removed. In some situations, for example, the
thinned wafer (without any support) must be transferred from the
vacuum chuck to the dicing frame before singulation. The thinned
wafer is highly susceptible to damage and/or breakage during this
transfer process. In situations where the wafer support is not
removed until after the wafer is attached to the dicing frame, the
wafer must still undergo singulation without any support. Moreover,
the thinned, singulated dies are extremely fragile and a number of
dies can be damaged and/or broken during removal from the dicing
frame and subsequent handling.
[0006] Another approach for addressing this drawback is to attach a
generally rigid, glass support member to the wafer to support the
wafer during the grinding process and subsequent handling. The
support member can be attached to the wafer using, for example, a
light-activated adhesive or another suitable adhesive material. In
several instances, a plurality of holes can be formed completely
through the support member to expose a portion of the wafer. These
holes are used to help facilitate removal of the adhesive material
from the wafer. After backgrinding, the wafer support member is
removed and the resulting thin wafer is ready for singulation and
further processing.
[0007] This system, however, also has several drawbacks. One
drawback is that the wafer support is generally removed before
singulation because it is extremely difficult to cut through the
glass support member during singulation. The holes through the
support member further complicate the singulation process and make
singulation with the glass support attached to the wafer
impracticable. Accordingly, the thinned wafer must undergo
singulation without any support. Another drawback with this system
is that many adhesive materials can be difficult to remove from the
wafer after processing. The removal process, for example, may
require a number of additional processing steps involving heat
and/or solvents. Accordingly, the wafer can be vulnerable to
damage, contamination, and/or breakage during removal of the
adhesive materials. Thus, there is a need to improve the handling
of microfeature workpieces during processing.
BRIEF DESCRIPTION OF THE DRAWINGS
[0008] FIGS. 1A-1J illustrate various stages of a method for
releasably attaching a sacrificial support member to a microfeature
workpiece in accordance with an embodiment of the invention.
[0009] FIG. 2 illustrates a stage in a method for releasably
attaching a sacrificial support member to a microfeature workpiece
in accordance with another embodiment of the invention.
DETAILED DESCRIPTION
A. Overview/Summary
[0010] The present invention is directed generally toward methods
for releasably attaching sacrificial support members to
microfeature workpieces and microfeature devices formed using such
methods. One particular embodiment, for example, is directed to a
method for processing a microfeature workpiece releasably attached
to a first support member. The workpiece includes a microelectronic
substrate, a plurality of microelectronic dies on and/or in the
substrate, and a sacrificial support member attached to an active
side of the substrate over the dies. The method can include
separating individual dies from the workpiece by cutting through
the sacrificial support member and the substrate while the
workpiece is attached to the first support member. The method can
then include attaching a singulated die and corresponding portion
of the sacrificial support member as a unit to a second support
member. The method can further include removing the sacrificial
support member from the die attached to the second support member
with a removal solution that attacks a material of which the
sacrificial support member is composed. In several embodiments, a
plurality of apertures can be formed at least partially through the
sacrificial support member to help facilitate removal of the
sacrificial support member from the die.
[0011] Another aspect of the invention is directed toward a
microfeature assembly. One embodiment of such an assembly includes
a microfeature workpiece including a microelectronic substrate
having a front side, a back side, and a plurality of
microelectronic dies at the front side. The assembly also includes
a sacrificial support member attached to the front side of the
substrate. The assembly further includes a first support member
carrying the substrate and the sacrificial support member. The
first support member is removably attached to the substrate to
temporarily support the substrate and the sacrificial support
member during singulation of the dies.
[0012] The term "microfeature workpiece" is used throughout to
include substrates upon which and/or in which microelectronic
circuits or components, data storage elements or layers, vias or
conductive lines, micro-optic features, micromechanical features,
and/or microbiological features are or can be fabricated using
microlithographic techniques. For example, microfeature workpieces
can be semiconductor wafers, glass substrates, insulated
substrates, or many other types of substrates. The term
"microfeature device" is used throughout to include microelectronic
devices, micromechanical devices, data storage elements, read/write
components, and other articles of manufacture. For example,
microfeature devices include imagers, SIMM, DRAM, flash-memory,
ASICs, processors, flip chips, ball-grid array chips, and other
types of electronic devices or components. Many specific details of
certain embodiments of the invention are set forth in the following
description and in FIGS. 1A-2 to provide a thorough understanding
of these embodiments. A person skilled in the art, however, will
understand that the invention may be practiced without several of
these details, and/or additional details can be added to the
invention. Well-known structures and functions have not been shown
or described in detail to avoid unnecessarily obscuring the
description of the embodiments of the invention.
B. Embodiments of Methods for Releasably Attaching Sacrificial
Support Members to Microfeature Workpieces
[0013] FIGS. 1A-1J illustrate various stages in one embodiment of a
method for releasably attaching a sacrificial support member to
microfeature workpieces. More specifically, FIGS. 1A-1J illustrate
stages of a method for releasably attaching a sacrificial support
member to a front side of the workpiece and, after additional
processing, removing the sacrificial support member without
damaging, cracking, or otherwise breaking the microelectronic dies
or other components of the workpiece.
[0014] FIG. 1A is a top plan view of a microfeature workpiece 100
at an initial processing stage. At this stage, a support material
which is described in detail below with respect to FIG. 1C has not
yet been deposited onto the workpiece 100. FIG. 1B is a side
cross-sectional view taken substantially along line 1B-1B of FIG.
1A. Referring to FIGS. 1A and 1B together, the workpiece 100
includes substrate 101 having a front or active side 102 and a back
side 104 facing opposite the front side 102. The workpiece 100
further includes a plurality of microelectronic dies 106 arranged
in a die pattern at the front side 102 of the substrate 101. The
dies 106 can be in and/or on the substrate 101. Each die 106 can
include integrated circuitry 108 (shown schematically) and a
plurality of pads 110 electrically coupled to the integrated
circuitry 108. In the illustrated embodiment, the pads 110 are
bond-pads at the front side 102 of the substrate 101. In other
embodiments, however, the pads 110 can include other types of
electrical connectors and/or can be positioned at other locations
on the dies 106. The dies 106 are separated from each other by a
plurality of streets or scribe lanes 112. The streets 112 are
generally aligned with one another to facilitate cutting with a
wafer saw or another suitable device. In other embodiments, the
dies 106 and/or the streets 112 can include other features and/or
have other arrangements.
[0015] FIG. 1C is a side cross-sectional view of the workpiece 100
after a support material layer 120 has been deposited onto the
front side 102 of the substrate 101. In one embodiment, for
example, the support material layer 120 can be formed separately
from the workpiece 100 and then one or more sheets of support
material can be applied onto desired portions of the workpiece 100
to form a sacrificial support member 130 that supports the
workpiece 100 to prevent breaking and/or excessive warping during
subsequent processing. The sheet(s) of support material can be
cured to a desired rigidity either before or after application.
Alternatively, the support material layer 120 can include a
flowable material that is deposited onto the front side 102 and
then cured to a generally non-flowable state and a desired rigidity
to form the sacrificial support member 130.
[0016] The support material layer 120 can be composed of polymeric
materials, ceramics, and/or other suitable materials. In one
embodiment, for example, the support material layer 120 can include
a heterogenic polymer material such as PDS.TM. commercially
available from Advanced Material Sciences of Hillsboro, Oreg. The
support material layer 120 can be deposited onto the front side 102
of the workpiece 100 using spin-on techniques, screen printing
processes, spraying techniques, brushing techniques, molding, a dip
bath, lamination, or other suitable processes. In several
embodiments, the coefficient of thermal expansion (CTE) of the
sacrificial support member 130 can be at least generally similar to
the CTE of the substrate 101 to help prevent excessive warping
and/or undesirable relative movement between the sacrificial
support member 130 and the substrate 101 during thermal
processing.
[0017] The support material layer 120 has an upper surface 122 at a
distance D from the front side 102 of the substrate 101. The
distance D can be selected, for example, based on the desired level
of support, the material used to form the support material layer
120, the thermal budget of the resulting assembly, the form factor
of the processing equipment, and/or other factors. The upper
surface 122 can be formed at the distance D from the front side 102
by depositing one or more sheets of support layer material 120
having a known thickness onto the substrate 101 or by planarizing
the support material layer 120 after application using suitable
planarization or grinding processes. In other embodiments,
additional processing may also be required to form the upper
surface 122 at the desired distance D from the front side 102.
[0018] After the support material layer 120 has been deposited or
attached to the front side 102 and cured (if necessary) to form the
sacrificial support member 130, the workpiece 100 is ready for
additional processing. In one embodiment, the additional processing
can include removing material from the back side 104 of the
substrate 101 to reduce its thickness. FIG. 1D, for example, is a
side cross-sectional view of the workpiece 100 after thinning. More
specifically, the substrate 101 has been thinned from a first
thickness T.sub.1 (shown in broken lines) to a second thickness
T.sub.2 less than the first thickness T.sub.1. In one embodiment,
for example, the substrate 101 can have a second thickness T.sub.2
of approximately 50-100 .mu.m. In other embodiments, however, the
thinned substrate 101 can have a different second thickness
T.sub.2. The material can be removed from the back side 104 by
grinding, etching, or other suitable processes.
[0019] After thinning, the back side 104 of the substrate 101 can
undergo further processing. In one embodiment, for example, a wafer
treatment (e.g., metallization, adhesive, etc.) can be applied to
at least a portion of the back side 104. The application of the
back side wafer treatment is an optional step that may be omitted
in several embodiments.
[0020] Referring next to FIG. 1E, the back side 104 of the
substrate 101 can be attached to a first support member 140. In one
aspect of this embodiment, the first support member 140 can include
an existing dicing support having a frame 142 carrying a
replaceable film 143 that can include an attachment device 144
(e.g., tape) that releasably adheres to the back side 104.
Accordingly, the first support member 140 can support the back side
104, while the sacrificial support member 130 continues to provide
support for the front side 102. In other embodiments, the first
support member 140 can include other suitable support devices.
[0021] Referring next to FIG. 1F, the workpiece 100 can be cut
along lines C-C to singulate the individual dies 106. The lines C-C
are generally aligned with the streets 112 (FIG. 1A) between the
dies 106. In one embodiment, a wafer saw or dicing blade 150 can be
used to form the incisions separating the dies 106. The saw 150 can
cut through the sacrificial support member 130, the substrate 101,
and in some cases at least a portion of the attachment device 144.
Although only a single wafer saw 150 is shown in FIG. 1F, in other
embodiments two or more wafer saws can be used to singulate the
dies 106. More specifically, in one embodiment a first wafer saw
having a first blade coarseness can be used to cut through the
sacrificial support member 130, while a second wafer saw having a
second blade coarseness less than the first blade coarseness can be
used to cut through the substrate 101 to singulate the dies
106.
[0022] In one aspect of this embodiment, the sacrificial support
member 130 remains attached to the front or active side 102 of each
die 106 both during and after singulation. One advantage of this
feature is that the sacrificial support member 130 can shield the
front side 102 of each die 106 from damage and/or contamination
during singulation, as well as providing support for the extremely
thin and fragile dies 106 during singulation and subsequent
processing.
[0023] Referring now to FIG. 1G, a conventional pick-and-place
apparatus 160 can be used to remove a first die 106a from the first
support member 140. In the illustrated embodiment, the attachment
device 144 remains attached to the film 143 so that no portion of
the attachment device 144 is removed with the first die 106a. In
another embodiment, however, at least a portion of the attachment
device 144 can be removed along with the first die 106a and can
later be removed from the first die 106a in a separate step. In
either embodiment, the first die 106a can be removed from the first
support member 140 while a second die 106b and a third die 106c
remain proximate to the first support member 140. The foregoing
removal process can then be repeated for the second die 106b, the
third die 106c, and other dies 106. In several embodiments, a
release agent (e.g., ultraviolet radiation) may be used to
facilitate removal of the dies 106 from the attachment device
144.
[0024] Referring next to FIG. 1H, one or more singulated dies 106
(e.g., the first die 106a) can be attached to a second support
member 170 (e.g., a lead frame, interposer substrate, circuit
board, flex tape, or the like) to form a microfeature device 180.
In the illustrated embodiment, the second support member 170
includes a first side 172 having a plurality of first contact pads
173 and a second side 174 having a plurality of second contact pads
175. A plurality of traces 176 extend through the second support
member 170 to electrically couple the first contact pads 173 to
corresponding second contact pads 175. An epoxy, tape, or other
suitable adhesive material (not shown) can be used to attach the
back side 104 of the die 106a to the first side 172 of the second
support member 170 (as shown by arrows D). If necessary, the
adhesive material between the die 106a and the second support
member 170 can be cured before further processing.
[0025] Referring now to FIG. 1I, the device 180 is exposed to a
removal solution to remove the sacrificial support member 130 from
the die 106a. In the illustrated embodiment, for example, the
device 180 is placed in a dip bath 190 including a solvent 192
(e.g., an acetone material) that attacks a material of which the
sacrificial support member 130 is composed (i.e., the support
material layer 120 (FIG. 1C)). The sacrificial support member 130
can include multiple constituents, and the solvent 192 can attack
some or all of the constituents. The solvent 192 at least partially
dissolves the sacrificial support member 130 such that the
sacrificial support member 130 is removed from the device 180,
leaving the die 106a and second support member 170 ready to undergo
further processing. It should be understood that when removing the
sacrificial support member 130 from the die 106a, residue from the
sacrificial support member 130 may remain on the die 106a in some
instances. Thus, in several embodiments the device 180 can
optionally undergo one or more additional post-processing steps to
remove any residual portions of the sacrificial support member 130
from die 106a after removing the device 180 from the dip bath
190.
[0026] In other embodiments, other types of removal solutions can
be used to remove the sacrificial support member 130 from the
device 180. The removal solutions, for example, can include aqueous
or non-aqueous solutions that attack the material of which the
sacrificial support member 130 is composed. Accordingly, the
selection of an appropriate removal solution is largely based on
the type of material used to form the sacrificial support member
130. In still other embodiments, the removal solution can be
applied or otherwise disposed onto the sacrificial support member
130 using a number of different methods (e.g., spraying processes,
brushing techniques, etc.) in addition to, or in lieu of, the dip
bath 190.
[0027] Referring next to FIG. 1J, the device 180 is ready for
additional processing and/or handling. In the illustrated
embodiment, for example, the die 106a can be electrically coupled
to the second support member 170 with a plurality of wire bonds 182
or other types of connectors extending between the pads 110 and
corresponding first contact pads 173 on the second support member
170. As such, the second support member 170 distributes signals
from the very small pads 110 on the die 106a to the larger array of
second contact pads 175 at the second side 174 of the second
support member 170. In other embodiments, the device 180 can
undergo other types of processing (e.g., encapsulation, etc.).
[0028] One feature of embodiments of the method described above
with reference to FIGS. 1A-1J is that the sacrificial support
member 130 can remain attached to the substrate 101 as the
substrate is thinned, attached to the first support member 140,
singulated, and as one or more individual dies 106 are subsequently
attached to the second support member 170 for additional
processing. An advantage of this feature is that the workpiece 100
is less likely to be damaged or broken as it is transferred from a
grinder or other thickness-reducing tool to the first support
member 140. In addition, the sacrificial support member 130 is
expected to enable extremely thin dies (e.g., dies having a
thickness of approximately 50-100 .mu.m) to survive removal (e.g.,
the "die pick" procedure) from the first support member 140 after
singulation. The sacrificial support member 130 accordingly
provides support to the substrate 101 and resulting dies 106
throughout processing until after the dies 106 are attached to the
second support member 170.
[0029] Another feature of embodiments of the method described above
is that the removal solution can relatively quickly and easily
remove the sacrificial support member 130 by attacking the material
of which the sacrificial support member 130 is composed. As
discussed previously, for example, the removal solution can include
aqueous or non-aqueous solvents that completely or substantially
dissolve away the sacrificial support member 130 without damaging
or negatively affecting the other components of the device 180. One
advantage of this feature is that the device 180 does not generally
require any post-processing cleaning to remove support member
residue from the device 180. Another advantage of this feature is
that it can increase throughput and reduce costs as compared with
conventional processes that require time-consuming processes and
expensive solvents for removing temporary support members.
[0030] Still another feature of embodiments of the method described
above is that the sacrificial support member 130 is releasably
attached over all or substantially all of the front side 102 of the
substrate 101. An advantage of this feature is that the die
features at the front side 102 are less likely to be damaged as the
workpiece 100 is processed because the sacrificial support member
130 provides support and protection. For example, the sacrificial
support member 130 can shield the sensitive and delicate components
of the dies 106 from incidental contact with surrounding tools,
machinery, and/or other components.
C. Additional Embodiments of Methods for Releasably Attaching
Sacrificial Support Members to Microfeature Workpieces
[0031] FIG. 2 illustrates a stage in a method for releasably
attaching a sacrificial support member to a microfeature workpiece
in accordance with another embodiment of the invention. More
specifically, FIG. 2 is a side cross-sectional view of a workpiece
200 after a support material layer 220 has been deposited onto the
workpiece. This stage of the method differs from the stage
described above with respect to FIG. 1C in that after depositing
the support material layer 220, a plurality of apertures 222 are
formed in the support material layer 220. In the illustrated
embodiment, for example, the apertures 222 are relatively small
openings that only extend partially through the support material
layer 220. In other embodiments, however, the apertures 222 can
include openings having different sizes or arrangements,
perforations, channels, trenches, or other types of openings that
extend either partially through the support material layer 220 or
completely through the support material layer 220 to the front side
102 of the substrate 101. The apertures 222 can be formed either
before or after the support material layer 220 is cured.
Furthermore, in cases where the support material layer 220 is a
separate component that is attached to the workpiece 200, the
apertures 222 can be formed in the support material layer 220
either before or after attachment. After forming the apertures 222,
the workpiece 200 can undergo additional processing steps that are
at least generally similar to those described above with reference
to FIGS. 1D-1J.
[0032] In one particular aspect of this embodiment, the apertures
222 are not aligned with the streets 112 between the individual
dies 106. One advantage of this feature is that the apertures 222
will not interfere with or otherwise affect the singulation process
described above with reference to FIG. 1F. In other embodiments,
however, one or more of the apertures 222 may be aligned with at
least a portion of the streets 112.
[0033] One feature of the apertures 222 extending at least
partially through the support material layer 220 (and a resulting
sacrificial support member 230 after curing of the support material
layer 220) is that the apertures 222 increase the surface area of
the sacrificial support member 230 and, accordingly, facilitate
faster removal of the sacrificial support member 230 with the
removal solution. The apertures 222, for example, are expected to
increase the rate at which the solvent bath (FIG. 1I) dissolves the
sacrificial support member 230 during processing. One advantage of
this feature is that it can increase throughput of processed
devices because it will take less time to remove the sacrificial
support member 230 from each device.
[0034] From the foregoing, it will be appreciated that specific
embodiments of the invention have been described herein for
purposes of illustration, but that various modifications may be
made without deviating from the invention. For example, the
sacrificial support member can be composed of other materials than
those described above, and the solvent used to remove the
sacrificial support member can be specifically tailored to attack
some or all of the materials from which the sacrificial support
member is composed. Aspects of the invention described in the
context of particular embodiments may be combined or eliminated in
other embodiments. Further, while advantages associated with
certain embodiments of the invention have been described in the
context of those embodiments, other embodiments may also exhibit
such advantages, and not all embodiments need necessarily exhibit
such advantages to fall within the scope of the invention.
Accordingly, the invention is not limited except as by the appended
claims.
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